The present study examined kanji errors in handwriting made by Japanese students and Australian learners of Japanese. First, a cognitive psychological model to explain the production of writing errors was proposed based upon the analysis of 374 writing errors of two-morpheme (kanji) compound words generated by Japanese students in spontaneous sentence writing situations. Despite the common assumption that kanji writing errors may not be related to the sounds of kanji characters (i.e., morphological phonology), the present study found that phonologically-related kanji writing errors were most numerous (60.0%), followed by orthographically-related errors (43.6%) and semantically-related errors (29.7%), including some overlap of these three types. Second, 408 kanji writing errors made by students learning Japanese in an Australian university were analyzed. Unlike the Japanese students, these subjects wrote more non-existing kanji and made orthographically-related mistakes rather than semantically- and phonologically-related errors. This result must be related to the level of kanji writing skills held by learners of Japanese. In light of these results, several suggestions were proposed for the methods of teaching kanji writing.